Bioinspired Materials—Graphene-enabled nicke…

Bioinspired Materials—Graphene-enabled nickel composites

Bioinspired engineering strategies rely on achieving the combined biological properties of strength and toughness inherent in nature. Tissue engineers and materials scientists therefore aim to construct intelligent, hierarchical biomimetic structures from limited resources. As a representative material, natural nacremaintains a brick-and-mortar structure that allows many viable toughening mechanisms on multiple scales. Such naturally occurring materials demonstrate an outstanding combination of strength and toughness, unlike any synthetic, engineered biomaterial.

In a recent study, Yunya Zhang and co-workers at the departments of Mechanical and Aerospace Engineering, Materials Science and Atom-Probe Tomography in the U.S. developed a bioinspired Ni/Ni3C composite to mimic nacre-like brick-and-mortar structure with Ni powders and graphene sheets. They showed that the composite achieved 73 percent increase in strength with only a 28 percent compromise in ductility to indicate a notable improvement in toughness.

In the study, the researchers developed optimized material of graphene-derived, nickel- (Ni), titanium- (Ti) and aluminum- (Al) based composites (Ni-Ti-Al/ Ni3C composite) that retained high hardness of up to 1000 °C. The materials scientistsunveiled a new method in the work to fabricate smart 2-D materials and engineer high-performance metal matrix composites. The composites displayed a brick-and-mortar structure via interfacial reactions to develop functionally advanced Ni-C based alloys for high-temperature environments. The results are now published in Science Advances.

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Atomic engineering with electric irradiation

Atomic engineering with electric irradiation

Atomic engineering can selectively induce specific dynamics on single atoms followed by combined steps to form large-scale assemblies thereafter. In a new study now published in Science Advances, Cong Su and an international, interdisciplinary team of scientists in the departments of Materials Science, Electronics, Physics, Nanoscience and Optoelectronic technology; first surveyed the single-step dynamics of graphene dopants. They then developed a theory to describe the probabilities of configurational outcomes based on the momentum of a primary knock-on atom post-collision in an experimental setup. Su et al. showed that the predicted branching ratio of configurational transformation agreed well with the single-atom experiments. The results suggest a way to bias single-atom dynamics to an outcome of interest and will pave the road to design and scale-up atomic engineering using electron irradiation.

Controlling the exact atomic structure of materials is an ultimate form of atomic engineering. Atomic manipulation and atom-by-atom assembly can create functional structures that are synthetically difficult to realize by exactly positioning the atomic dopants to modify the properties of carbon nanotubes and graphene. For example, in quantum informatics, nitrogen (N) or phosphorous (P) dopants can be incorporated due to their nonzero nuclear spin. To successfully conduct experimental atomic engineering, scientists must (1) understand how desirable local configurational change can be induced to increase the speed and the success rate of control, and (2) scale up the basic unit processes into feasible structural assemblies containing 1 to 1000 atoms to produce the desired functionality.

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Colorful solution to a chemical industry bot…

Colorful solution to a chemical industry bottleneck

The nanoscale water channels that nature has evolved to rapidly shuttle water molecules into and out of cells could inspire new materials to clean up chemical and pharmaceutical production. KAUST researchers have tailored the structure of graphene-oxide layers to mimic the hourglass shape of these biological channels, creating ultrathin membranes to rapidly separate chemical mixtures.

“In making pharmaceuticals and other chemicals, separating mixtures of organic molecules is an essential and tedious task,” says Shaofei Wang, postdoctoral researcher in Suzana Nuñes lab at KAUST. One option to make these chemical separations faster and more efficient is through selectively permeable membranes, which feature tailored nanoscale channels that separate molecules by size.

But these membranes typically suffer from a compromise known as the permeance-rejection tradeoff. This means narrow channels may effectively separate the different-sized molecules, but they also have an unacceptably low flow of solvent through the membrane, and vice versa—they flow fast enough, but perform poorly at separation.

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Stickier than expected: Hydrogen binds to gr…

Stickier than expected: Hydrogen binds to graphene in 10 femtoseconds

Bound for only ten quadrillionths of a second

Graphene is celebrated as an extraordinary material. It consists of pure carbon, only a single atomic layer thick. Nevertheless, it is extremely stable, strong, and even conductive. For electronics, however, graphene still has crucial disadvantages. It cannot be used as a semiconductor, since it has no bandgap. By sticking hydrogen atoms to graphene such a bandgap can be formed. Now researchers from Göttingen and Pasadena (USA) have produced an “atomic scale movie” showing how hydrogen atoms chemically bind to graphene in one of the fastest reactions ever studied.

The international research team bombarded graphene with hydrogen atoms. “The hydrogen atom behaved quite differently than we expected,” says Alec Wodtke, head of the Department of Dynamics at Surfaces at the Max Planck Institute (MPI) for Biophysical Chemistry and professor at the Institute of Physical Chemistry at the University of Göttingen. “Instead of immediately flying away, the hydrogen atoms ‘stick’ briefly to the carbon atoms and then bounce off the surface. They form a transient chemical bond,” Wodtke reports. And something else surprised the scientists: The hydrogen atoms have a lot of energy before they hit the graphene, but not much left when they fly away. Hydrogen atoms lose most of their energy on collision, but where does it go?

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No ink needed for these graphene artworks: Art…

No ink needed for these graphene artworks: Artist employs Rice University lab’s laser-induced graphene as medium for ultramodern art

When you read about electrifying art, “electrifying” isn’t usually a verb. But an artist working with a Rice University lab is in fact making artwork that can deliver a jolt.

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The Rice lab of chemist James Tour introduced laser-induced graphene (LIG) to the world in 2014, and now the researchers are making art with the technique, which involves converting carbon in a common polymer or other material into microscopic flakes of graphene.

LIG is metallic and conducts electricity. The interconnected flakes are effectively a wire that could empower electronic artworks.

The paper in the American Chemical Society journal ACS Applied Nano Materials – simply titled “Graphene Art” – lays out how the lab and Houston artist and co-author Joseph Cohen generated LIG portraits and prints, including a graphene-inspired landscape called “Where Do I Stand?”

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Decoupled graphene thanks to potassium bromi…

Decoupled graphene thanks to potassium bromide

The use of potassium bromide in the production of graphene on a copper surface can lead to better results. When potassium bromide molecules arrange themselves between graphene and copper, it results in electronic decoupling. This alters the electrical properties of the graphene produced, bringing them closer to pure graphene, as reported by physicists from the universities of Basel, Modena and Munich in the journal ACS Nano.

Graphene consists of a layer of carbon atoms just one atom in thickness in a honeycomb pattern and is the subject of intensive worldwide research. Thanks to its high level of flexibility, combined with excellent stability and electrical conductivity, graphene has numerous promising applications – particularly in electronic components.

Molecules for decoupling

Graphene is often produced via a chemical reaction on metallic surfaces in a process known as chemical vapor deposition. The graphene layer and the underlying metal are then electrically coupled, which diminishes some of the special electrical properties of graphene. For use in electronics, the graphene has to be transferred onto insulating substrates in a multistep process, during which there is a risk of damage and contamination.

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Graphene sponge helps lithium sulphur batter…

Graphene sponge helps lithium sulphur batteries reach new potential

To meet the demands of an electric future, new battery technologies will be essential. One option is lithium sulphur batteries, which offer a theoretical energy density more than five times that of lithium ion batteries. Researchers at Chalmers University of Technology, Sweden, recently unveiled a promising breakthrough for this type of battery, using a catholyte with the help of a graphene sponge.

The researchers’ novel idea is a porous, sponge-like aerogel, made of reduced graphene oxide, that acts as a free-standing electrode in the battery cell and allows for better and higher utilisation of sulphur.

A traditional battery consists of four parts. First, there are two supporting electrodes coated with an active substance, which are known as an anode and a cathode. In between them is an electrolyte, generally a liquid, allowing ions to be transferred back and forth. The fourth component is a separator, which acts as a physical barrier, preventing contact between the two electrodes whilst still allowing the transfer of ions.

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3-D printing electrically assisted, nacre-in…

3-D printing electrically assisted, nacre-inspired structures with self-sensing capabilities

Nacre, also known as mother of pearl is a composite, organic-inorganic material produced in nature in the inner shell layer of molluscs and the outer coating of pearls. The material is resilient and iridescent with high strength and toughness, resulting from its brick-and-mortar-like architecture. Lightweight and strong materials are of interest in materials science due to their potential in multidisciplinary applications in sports, aerospace, transportation and biomedicine. In a recent study, now published in Science Advances, Yang Yang and co-workers at the interdisciplinary departments of Systems Engineering, Chemical, Biomedical and Aerospace Engineering at the University of Southern California, developed a route to build nacre-inspired hierarchical structures with complex 3-D shapes via electrically assisted 3-D printing.

To create a brick-and-mortar-like structure in the work, they aligned graphene nanoplatelets (GNs) as bricks in the electric field (433 V/cm) during 3-D printing and included the polymer matrix as a mortar. The bioinspired 3-D printed nacre with aligned GNs (2 percent weight) were lightweight (1.06 g/cm3), albeit with specific toughness and strength similar to the natural nacre counterpart. The 3-D printed lightweight, smart armor aligned GNs could sense surface damage to exert resistance change during electrical applications. The study highlighted interesting possibilities for bioinspired nanomaterials with hierarchical architecture tested in a proof-of-principle, mini smart helmet. Projected applications include integrated mechanical reinforcement, electrical self-sensing capabilities in biomedicine, aerospace engineering as well as military and sports appliances.

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Squeezed nanocrystals: A new model predicts th…

Squeezed nanocrystals: A new model predicts their shape when blanketed under graphene

In a collaboration between the U.S. Department of Energy’s Ames Laboratory and Northeastern University, scientists have developed a model for predicting the shape of metal nanocrystals or “islands” sandwiched between or below two-dimensional (2D) materials such as graphene. The advance moves 2D quantum materials a step closer to applications in electronics.

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Ames Laboratory scientist are experts in 2D materials, and recently discovered a first-of-its-kind copper and graphite combination, produced by depositing copper on ion-bombarded graphite at high temperature and in an ultra-high vacuum environment. This produced a distribution of copper islands, embedded under an ultra-thin “blanket” consisting of a few layers of graphene.

“Because these metal islands can potentially serve as electrical contacts or heat sinks in electronic applications, their shape and how they reach that shape are important pieces of information in controlling the design and synthesis of these materials,” said Pat Thiel, an Ames Laboratory scientist and Distinguished Professor of Chemistry and Materials Science and Engineering at Iowa State University.

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